A blunder at a NHS fertility clinic has reportedly led to a white couple having black twins as a result of IVF treatment.

Although the full facts of the case have yet to emerge, it is suggested that either an embryo created from eggs and sperm from a black couple - or sperm from a black man - was used by error in the treatment of the white couple.

"When you do these things you have to make sure you try and match the physical characteristics.

"Or, it could be a rare disorder with pigmentation of the skin. This is more common where you have a black couple with a white baby. It could be an indication of a disease. You would not discover this while the woman was pregnant.

Q: How tight are the controls to stop such mistakes happening?

Professor Taranissi said: "I would say this is extremely unlikely to happen. There are always double checks on every step of the way.

"With insemination, checking for eggs and putting the embryos back is always checked by two people to make sure these kind of incidences do not happen."

Labs in fertility clinics use colour-coding, date of birth, and name checks.

Unless all of these tally up on patient and embryo, the treatment does not proceed.

In some labs, two embryologists have to be on hand at the same time to double-check each other's work.

Professor Robert Winston, from Hammersmith Hospital in London, said: "That is about as failsafe as you can get."

But he said that ultimately, errors could happen in any system involving humans.

They check that clinics have procedures in place to double-check the
identification of people undergoing treatment, the sperm and eggs at the time of
insemination and the embryos and the patient at the time of embryo transfer.

The HFEA, in a statement issued today, said this "should minimise the risk of
the wrong sperm, eggs or embryos being used".

Q: How many IVF treatments are carried out in this country?

A: There are just under 40,000 cycles of IVF done in this country every year.

Q: What is the legal position regarding who will keep the babies?

These are uncharted legal waters in the UK - it is possible that there could be a legal struggle over the future of these twins - but nothing is yet certain.

The law at the moment states that the woman who carries the child is the biological mother - but this may be tested in court.

Q: What reassurances can be given couples embarking on IVF treatment?

Professor Taranissi said: "I would say this is very rare and, without knowing the details of this case, it is going to be anybody's guess why this happened. It is very rare.

"IVF came in 10-11 years ago and there are 40,000 cycles each year and this is the first time we have heard about this."